The hydraulic fracturing of oil wells was started in the late Nineteen Forties as a means of oil well stimulation when trying to extend the economic life of a depleting oil well. Most oil wells, at that time, were driven vertically. The placement of shaped explosive charges, in thin wall casings, was limited to these explosive charges being placed in predetermined, hydrocarbon pay zones, and mostly in sand formations. The shaped explosive charges were ignited to create fissures or channels in these zones. A mixture of pressurized water and sand is pumped into the wellbore as a means of well stimulation.
This practice of well stimulation continues in vertically driven wells to this day. It wasn't until Mitchell Energy, in the mid-nineteen nineties utilized two newly developed technologies, changed the way unconventional, insitu hydrocarbon shale could be produced economically. The first new technology utilized was the development of steerable and controllable drilling techniques that could change the direction of a drill bit going in a vertical direction and rotating it into a horizontal direction. This rotation could be accomplished with a reasonably short bending radius and the drill bit could then continue to drill horizontally for a considerable distance into the shale formation.
The second technology that was needed involved the development of higher pressure fracturing pumps that were capable of achieving water pressures in the range of nine thousand to ten thousand pounds per square inch range at the surface. The answer was the development of fracturing pumps that could achieve these pressure levels with positive displacements. Both technologies are essential for the economic extraction of hydrocarbon gases and liquids in hard and soft shale formations. Companies today are producing gaseous and liquid hydrocarbons and use mostly chemical products to control the growth of micro-organisms. These could eventually migrate into potable water aquifers.
Currently, it is common practice to kill micro-organisms that are in the water mixture, either initially or insitu, by chemical or other types of biocides, so that the gaseous and liquid hydrocarbons that are trapped in the oil shale's matrix formation can flow freely into the channels and fissures vacated by the flow-back water mixture. Also, the channels created by the fracturing process must be kept open by the proppants that are initially carried into the fissures in the fracture zones by the injected water mixture. If the micro-organisms are not killed they will multiply, rapidly; and, if they remain in the fissures, they will grow and reduce or entirely block the flow hydrocarbons from these fissures. Another significant micro-organism type problem is the possible presence of a strain of microbes that have an affinity for seeking out and digesting any free sulfur or sulfur bearing compounds and producing hydrogen sulfides that must be removed from any product gas stream because it is a highly dangerous and carcinogenic material. All these types of micro-organisms must be destroyed if this type of problem is to be avoided.
In addition to the possibility of micro-organisms multiplying and blocking the flow of hydrocarbon product, the presence of dissolved solids in the water solution can also be a problem in the injected water mixture. They can deposit themselves as scale or encrustations in the same flow channels and fissures. These encrustations, if allowed to be deposited in these channels, will also reduce or block the flow of hydrocarbons to the surface. In order to avoid this condition, attempts are made in current industry practice to have the dissolved solids coalesce and attach themselves to the suspended or other colloidal particles present in the water mixture to be removed before injection in the well; however, those efforts are only partly effective. See, e.g. Denny, Dennis. (2012 March). Fracturing-Fluid Effects on Shale and Proppant Embedment. JPT. pp. 59-61. Kealser, Vic. (2012 April). Real-Time Field Monitoring to Optimize Microbe Control. JPT. pp. 30, 32-33. Lowry, Jeff, et al. (2011 December). Haynesville trial well applies environmentally focused shale technologies. World Oil. pp. 39-40, 42. Rassenfoss, Stephen. (2012 April). Companies Strive to Better Understand Shale Wells. JPT. pp. 44-48. Ditoro, Lori K. (2011). The Haynesville Shale. Upstream Pumping Solutions. pp. 31-33. Walser, Doug. (2011). Hydraulic Fracturing in the Haynesville Shale: What's Different? Upstream Pumping Solutions. pp. 34-36. Denney, Dennis. (2012 March). Stimulation Influence on Production in the Haynesville Shale: A Playwide Examination. JPT. pp. 62-66. Denney, Dennis. (2011 January). Technology Applications. JPT. pp. 20, 22, 26. All of the above are incorporated herein by reference for all purposes.
In recent years, the oil industry has tried to develop a number of ways to address these concerns. The use of ultra violet light in conjunction with reduced amounts of chemical biocide has proven to be only partially effective in killing water borne micro-organisms. This is also true when also trying to use ultra-high frequency sound waves to kill micro-organisms. Both these systems, however, lack the intensity and strength to effectively kill all of the water-borne micro-organisms with only one weak short time residence exposure and with virtually no residual effectiveness. Both systems need some chemical biocides to effectively kill all the water borne micro-organisms that are in water. Also, some companies use low-frequency or low-strength electro-magnetic wave generators as biocide/coalescers; however, these too have proven to be only marginally effective.
Therefore, an object of further examples is to economically address and satisfactorily resolve some of the major environmental concerns that are of industry-wide importance. Objects of still further examples are to eliminate the need for brine disposal wells, eliminate the use of toxic chemicals as biocides for micro-organism destruction, or for scale prevention, and the recovery of all flow-back or produced water for reuse in subsequent hydraulic fracturing operations. Examples of the invention provide technically sound and economically viable solutions to many of the public safety issues that have concerned the industry in hydraulic fracturing.